> >>>By distributing callers across multiple scanned frequencies, the > incidence of multiple callers colliding on a single frequency is > reduced. Such collisions prevent the PMBO from connecting with any > of the competing callers, increasing time-from-request-to- > connection. If the callers cannot hear each other, then they don't > know to back off and the collision is extended in time -- further > increasing time-from-request-to-connection for all callers.
If the PMBO is busy passing traffic on another frequency, he is not scanning, so the really significant delay in time-from-request-to-connection is always waiting for him to finish passing traffic and resume scanning. Once he resumes scanning, he is going to connect with the strongest caller that he can hear, even if there are multiple callers. The only way he would be unable to connect is if all callers were at the same strength AND timing. So, using scanning has a negligible improvement in the time-from-request-to-connection, and that would only apply to ONE of the multiple callers - the one that was successful. For the others, that time might be infinite. > > > > Because the PMBO stations are not allowed to broadcast, the client > MUST call a specific PMBO. If he does that on any of the alternate > frequencies of the PMBO, he cannot connect until the PMBO is > finished passing traffic on the frequency being used. The client > station may transmit continusouly for a connect, but he will not > achieve one until the PMBO finishes passing traffic and starts > scanning again and picks up the client station's transmission. > > > > The result of the scanning is that the Winlink client station > is "holding the frequency" for his own use and nobody can use it or > capture it while he is doing that. > > >>>If callers (which are always attended) refrain from initiating a > request on a frequency that is already busy or becomes busy after an > unsuccessful request, then the caller is not guilty of holding the > frequency. As I mentioned in my previous post, the problem is that a > Winlink-on-Pactor PMBO has no busy detector, and thus threatens QSOs > on any of its scanning frequencies with hidden-transmitter QRM. > Knowledgable operators wishing a QRM-free QSO would therefore tend > to avoid any frequency scanned by a Winlink-on-Pactor PMBO. Is a > PMBO "holding" its scanning frequencies? Legally, no; pragmatically, > yes. 14076.9 may currently be clear, but there's no way I'll call CQ > there. With scanning, the caller is holding the frequency whether or not he is "guilty" of doing so, which would only be the case if he were aware that the PMBO was busy and he kept calling. He may not be "guilty" of holding the frequency, but he is accidentally holding the frequency nevertheless, because he thinks it is clear and the PMBO is listening for a connect, when, in reality, that is not true. The PBMO is not listening (on the alternate frequency) for a connect. Eliminating scanning eliminates this problem. The hidden-transmitter problem is certainly real, but ONLY after the PMBO has been triggered to transmit. In practice, the MAJORITY of QRM, as you can easily observe on the waterfall, is not the hidden-transmitter, but the client stations transmitting, breaking up the QSO, waiting for a while, and doing the same thing over again. If they do trigger a PMBO to transmit, then the QRM generally becomes much worse, as can also be seen on the waterfall. If there were no scanning, then the calling client station would not be repeatedly calling on the alternate frequency, even if he could not detect weaker activity on the frequency, because he would be monitoring the same frequency the PMBO he wishes to contact is currently using. In fact, HALF of all the Winlink advertises frequencies would NEVER be used by Winlink if there were no scanning, unless the number of PMBO's doubled and scanning was eliminated. If half of the frequencies currently advertised by Winlink were eliminated from their system, then half of the PMBO's could be reassigned to the vacated frequencies, leaving a large block of frequencies available for everyone else to use without fear of a PMBO station popping up on top of their QSO like they do now. So, the real fair solution to the problem is: 1. Eliminate scanning. 2. Reassign PMBO to frequencies in a contiguous block, with a geographical separation of PMBO's on alternate frequencies, as much as possible, to lessen the chance of adjacent channel interference. This keeps the Winlink traffic handling capacity the same, frees up space for others to use, and eliminates the QRM to others by PMBO stations. The time-from-request-to-connection would not be noticeably different, if there is any at all. 73, Skip KH6TY The K3UK DIGITAL MODES SPOTTING CLUSTER AT telnet://208.15.25.196/ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
